Today the Bitcoin network is restricted to a sustained rate of 7 tps by some artificial limits. These were put in place to stop people from ballooning the size of the block chain before the network and community was ready for it. Once those limits are lifted, the maximum transaction rate will go up significantly.

I also found this talk by Peter Todd from keepbitcoinfree.org on using off blockchain transactions to avoid hitting the main block chain with the full transaction load which was followed by good Q&A